Vehicle immobiliser/alarm

ABSTRACT

A security system having security devices with hierarchical levels of access provided to coded keys which may be hand held transmitter units, is disclosed. The levels of access are master which is restricted to the manufacturer, seller and installer, supervisor which can be allocated to a site, and user which is usually specific to one security device only. The security devices can be programmed to be responsive to all of the supervisor coded keys and/or user coded keys, or a user coded key only. The security system can be used in a method of securing all vehicles at a car sales, where all of the vehicles can have their security devices programmed to be responsive to supervisor coded keys specific to the car sales site. When a vehicle is sold, its security device can be reprogrammed to be responsive to specific user coded keys only.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority from AustralianProvisional Application No. 2002951399, filed 16 Sep. 2002 andAustralian Provisional Application No. 2002951402, filed 16 Sep. 2002,the teachings of each of which are incorporated herein by reference.

FIELD OF THE INVENTION

[0002] This invention relates to a vehicle alarm or immobiliser, and inparticular a vehicle immobiliser or alarm of the type incorporating acoded key for verification of control signals used to disarm (andpreferably also to arm) the immobiliser or alarm.

BACKGROUND ART

[0003] In a vehicle security system the method of deactivating is almostalways by means of a coded key. The coded key may be a radio remote, aproximity device or a contact type such as a plug which is inserted intoa socket. In order to offer security the number of codes should be high.In most modem security systems taking into account various encryptionmethods, the number of different codes can effectively be in thebillions. Often the coded key is provided as a binary code which isserially transmitted to an immobiliser or car alarm. In modem securitysystems a transmitted code can have 64 bits, and taking into accountvarious encryption methods, the number of different codes can be in thebillions. In addition there is a system of encryption which uses“code-hopping”, where the transmitted code has a portion thereof whichincrements by a predetermined amount determined by an algorithm in thecoded key. The immobiliser responsive to the coded key incorporating thecode-hopping technology includes a processor which is able to predictahead a large number of increments, so that the immobiliser remainsresponsive to the coded key in the event that the coded key is caused totransmit several increments out of range of the immobiliser.

[0004] The security system is, in normal use, responsive to a uniqueallocated user code, so that the security system can be disabled andenabled by the owner of the vehicle in which it is installed. This usercode is determined and programmed into the coded key during manufacture,and into the security system either during manufacture or alternativelythe security system can learn the user code from the coded key, byplacing the security system into a learning mode.

[0005] Motor vehicle dealers usually have many cars at one time in theircar yard. The typical practice is to have the keys to the vehiclesstored in a central secure location, such as in the sales office. Staffwishing to demonstrate a vehicle to a potential customer must retrievethe keys and any coded key remote control (or other type of coded key)for the vehicle beforehand.

[0006] It is an object of this invention to provide a system and methodthat can provide security to vehicles in a car yard or likeestablishment, and obviate the above difficulty.

[0007] Throughout the specification, unless the context requiresotherwise, the word “comprise” or variations such as “comprises” or“comprising”, will be understood to imply the inclusion of a statedinteger or group of integers but not the exclusion of any other integeror group of integers.

DISCLOSURE OF THE INVENTION

[0008] The applicant has provided an improvement in security systems forvehicles which provides in a security system for one or more of aplurality of available supervisor codes, which allows one or more uniquesupervisor codes to be allocated to a motor vehicle dealer. The securitysystem with unique supervisor code(s) allocated, is then responsive torespective supervisor code coded key(s), with limited permissions forcontrol of security system features. This allows one or more uniquesupervisor codes to be allocated to a motor vehicle dealer.

[0009] The applicant has provided, in a preferred arrangement, animprovement in security systems for vehicles which provides in asecurity system a master code having full permissions for control ofsecurity system features using a master code coded key, a second tier ofa plurality of supervisor codes from which one or more may be allocatedand enabled, the enabled supervisor code(s) having limited permissionsfor control of security system features using one or more supervisorcode coded keys. This also allows a unique second tier supervisor codeto be allocated to a motor vehicle dealer.

[0010] The security system also of course, includes facility for one ofa plurality of possible user codes to be allocated and enabled, fornormal use by a final consumer/user using a user code coded key.

[0011] Either arrangement described above allows a single uniquesupervisor coded key to be used to disable all of the second tiersupervisor code keyed vehicle security systems fitted to vehicles on thevehicle dealer car lot. This feature saves considerable time for a carlot operator wanting to demonstrate a car, as the ignition keys cansafely be left in the vehicles.

[0012] Either arrangement may include a feature whereby the enabling ofa supervisor code disables a user code, and vice versa.

[0013] In accordance with one aspect of the invention there is provideda security system including a security device arranged to exert controlover a predetermined function, said security device being responsive toa coded key to exert control over said predetermined function, saidcoded key and said security device communicating using a data string ofa predetermined format, wherein said data string includes apredetermined portion thereof having settable values, wherein saidsettable values when within a first predetermined range of valuescorrespond to user codes assigned to user coded keys for said securitydevice, and said settable values when within a second predeterminedrange of values correspond to supervisor codes assigned to supervisorcoded keys for said security device, and said settable values whenwithin a third predetermined range of values correspond to user codesassigned to master coded keys for said security device, wherein saidsecurity system includes programming means allowing said security deviceto be programmable to be responsive to one or more said supervisor codedkeys and/or one or more said user coded keys, or one or more of saiduser coded keys only, wherein said supervisor coded keys have anintermediate level of access to said programming means between the levelof access of said master coded keys and said user coded keys.

[0014] Typically, the supervisor coded keys can be provided toauthorised personnel, while the user coded keys would be provided tousers having more limited access. For example, in security systems suchas vehicle immobilisers, supervisor coded keys could be provided to carsales staff, while user coded keys could be provided to customers whoultimately purchase the vehicle. In such an arrangement, user coded keysare always coded specifically for a particular security device. Themaster coded keys have a greater level of access than the supervisorcoded keys, and are usually restricted to the security systemmanufacturer, seller, and installer. It should be understood that theremay be one or more master coded keys.

[0015] Preferably said security system includes programming meansallowing said security device to be programmable to be responsiveexclusively to one or more said supervisor coded keys, or exclusively toone or more of said user coded keys only.

[0016] The second range of values may be conveniently limited to 65534possible values. Within the data string there are a number ofcombinations available, based on other portions of code outside of thesecond range making up the remainder of the data string. In motorvehicle dealerships, this allows for 65534 different possible dealerscodes, and a plurality of different remote controls incorporatingidentical second strings, for use by staff within the dealership.

[0017] In accordance with a second aspect of the invention there isprovided a method of providing security against theft to a plurality ofvehicles at a site, said method including steps of providing a securitysystem as hereinbefore described, the security system comprising aplurality of security devices for selectively immobilising and enablingoperation of vehicles, and installing said security devices in vehiclesat said site, wherein all of said security devices are selectablyresponsive to one or more coded keys specific to said site.

[0018] Preferably said security devices are selectably responsive tosaid coded keys by being programmed to recognise code transmittedthereby.

[0019] Also in accordance with a second aspect of the invention there isprovided a method of providing security against theft to a plurality ofvehicles at a site, said method including steps of providing a securitysystem as hereinbefore described, allocating said supervisor coded keyswith supervisor codes specific to said site, installing a said securitydevice in each of said vehicles at said site, and actuating saidprogramming means to program each said security device to be responsiveto said supervisor coded keys allocated to said site for selectivelyimmobilising and enabling operation of vehicles, wherein all of saidsecurity devices are selectably responsive to one or more supervisorcoded keys allocated to said site.

[0020] Preferably said security devices are responsive to saidsupervisor coded keys to actuate said programming means to program saidsecurity device to be solely responsive to code transmitted by one ormore specific said user coded keys.

[0021] Preferably said security devices are incorporated in relays usedto control a circuit essential for operation of the vehicle. An exampleof such a relay is described in the applicant's co-pending patentapplication PCT/AU01/01075, the contents of the specification for whichare incorporated herein by cross-reference.

[0022] With this arrangement, a site can be provided with one or morecoded keys, and security devices, responsive to the coded keys, forfitting into vehicles. With two or more adjacent sites having the samesystem in place, the security devices only respond to coded keys at thecorrect site.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] A preferred embodiment of the invention will now be described inthe following description of a vehicle immobiliser made with referenceto the drawings, in which:

[0024]FIG. 1 is a block schematic of a coded key for use with theembodiment, and

[0025]FIG. 2 is a block schematic of a security device incorporating theembodiment.

BEST MODES(S) FOR CARRYING OUT THE INVENTION

[0026] A security system having security devices with hierarchicallevels of access provided to coded keys which may be hand heldtransmitter units, is provided by the embodiment. The levels of accessare master which is restricted to the manufacturer, seller andinstaller, supervisor which can be allocated to a site such as a carsales yard, and user which is usually specific to one security deviceonly. The security devices can be programmed to be responsive to all ofthe supervisor coded keys and/or user coded keys, or a user coded keyonly. The security system can be used in a method of securing allvehicles at a car sales, where all of the vehicles can have theirsecurity devices programmed to be responsive to supervisor coded keysspecific to the car sales site. When a vehicle is sold, its securitydevice can be reprogrammed to be responsive to specific user coded keysonly.

[0027] The security system according to the embodiment, for a vehicle,has a coded key in the form of a radio remote key, shown in FIG. 1. Theradio remote key has a press button switch 11 used by a person todisable immobilization and enable immobilization of the vehicle to whichthe security device is fitted. The switch 11 is interfaced to aprocessor 13. The processor 13 is connected to output a serial code to aradio transmitter circuit 15, both the processor 13 and radiotransmitter circuit 15 being powered by a power supply in the form of abattery 17. The processor 13 is responsive to the switch 11, and causesthe transmitter circuit 19 to transmit a serial code in accordance witha program contained in ROM in the processor 13. The serial code includesa portion of rolling code which is incremented according to an algorithmcontained in the program in the processor 13, providing so called“code-hopping”. Code-hopping prevents evesdropping on the transmittedserial code, and unauthorized reproduction of a previously transmittedcode being used to subsequently disable immobilization and steal thevehicle.

[0028] The security device, shown generally in FIG. 2, has a radioreceiver circuit 21 which receives the radio signal transmitted from theradio remote key. The radio receiver circuit has a processor 23connected to the receiver circuit 21, and receives the serial code fromthe receiver circuit 21. The processor 23 controls two relays 25 via acontrol circuit 27, the relays 25 in use being wired into circuitsrequired for normal vehicle operation, such as the ignition circuit,fuel injection control circuitry, fuel pump, or starter motor actuationcircuitry.

[0029] The processor 23 has both RAM 29 and ROM (not shown) inaccordance with usual practice. A program installed on ROM in theprocessor 23 toggles the relays 25 between states, to disableimmobilization and enable immobilization of the vehicle (enable anddisable operation respectively of the vehicle). The program alsoauto-arms the immobilizer after the vehicle has been switched off for apredetermined time (usually about 30 to 60 seconds) or hasn't beenstarted after the predetermined time. The program includes an algorithmto predict ahead for a large number of possible codes incrementedaccording to the algorithm contained in the program in the processor 13in the radio remote key.

[0030] In addition to this, the processor 23 in the security device iscapable of “learning” codes from radio remote keys, when set in acondition to allow this.

[0031] The embodiment of the invention provides a vehicle dealershipsecurity system in the form of vehicle immobilisers for all cars on acar lot using identical supervisor codes. Any vehicle arriving on thelot can be fitted with a compatible security system, which is thenprogrammed with the dealer's supervisor code. This enables all of thevehicles in the dealership to be operated by supervisor code coded keyswhich can be allocated to staff. With such an arrangement, all vehicleson the lot are protected, ignition keys can be left in the vehiclesallowing rapid demonstration to a potential customer, and the securitysystem can then be sold with the vehicle as it is already installed.

[0032] With the arrangement of the invention, there are a number ofdifferent code permutations available as master, supervisor, and usercodes, as set out in the following table: Code permutations Used byMaster 1 Manufacturer only Supervisor 65,533 Dealership User4,294,901,757 Purchaser Rolling 4,294,967,925 Internal only

[0033] The master code is a closely guarded code, which is only used bythe manufacturer. In practise there would be at least one code availablefor each manufacturer, so a number of different manufacturers couldutilise the invention and not ordinarily be able to access control ofthe opposition's product.

[0034] The master code uses 4 reserved bytes that are never repeated inany of the other type of codes. The master code coded key is usedprimarily to program supervisor codes, and may be used to program usercodes recognised by the security devices installed in vehicles.

[0035] The following table represents a serial code string as producedby a master code coded key: FIXED CODES ROLLING CODES BYTE 0 BYTE 1 BYTE2 BYTE 3 BYTE 4 BYTE 5 BYTE 6 BYTE 7 11 h 22 h 33 h 44 h XX XX XX XX

[0036] The values contained in bytes 0-3 are 11h, 22h, 33h, 44hrespectively. The first two bytes specify that this code is a“supervisor” code, however in combination with the 33h & 44h furtherspecifies this is the “Master” code.

[0037] The supervisor code uses 11h and 22h in bytes 0 & 1 respectively,same as the master. However the supervisor codes have another 64,000+combinations specified by bytes 2 & 3. The value combination of 33h &44h in bytes 2 & 3 is the only illegal code for a supervisor code.Supervisor code coded keys are then used to program user codesrecognised by the security devices installed in vehicles. Any givensupervisor code coded key cannot program user codes into a securitydevice coded with a different supervisor code coded key.

[0038] The following table represents a serial code string as producedby a supervisor code coded key: FIXED CODES ROLLING CODES BYTE 0 BYTE 1BYTE 2 BYTE 3 BYTE 4 BYTE 5 BYTE 6 BYTE 7 11 h 22 h ?? ?? XX XX XX XX

[0039] The user code is the code programmed at the lowest level. Usercode coded remotes cannot program any other type of remote to berecognised by a security device installed in a vehicle.

[0040] User codes may use any combination of values in any byte exceptfor 11h & 22h in bytes 0 & 1 respectively.

[0041] The following table represents a serial code string as producedby a supervisor code coded key: FIXED CODES ROLLING CODES BYTE 0 BYTE 1BYTE 2 BYTE 3 BYTE 4 BYTE 5 BYTE 6 BYTE 7 \\ \\ XX XX XX XX XX XX

[0042] The rolling code part of any code is the continually changingbytes, which provide the encryption for all codes. They are not recordedby the “real world” because they change each time the remote button ispressed.

[0043] Operation of a most preferred embodiment of the security systemaccording to the invention will now be described.

[0044] In the electronic vehicle security system a number ofdeactivation codes are stored in non volatile memory, usuallyelectrically erasable memory. In normal operation, as perceived by afinal consumer, when a user code is received by the processor (from anexternal user code coded key) it is compared with the user code storedin memory. If a match is found the system will deactivate.

[0045] If a supervisor code is received the same holds true but inaddition to checking the received code against unique codes stored inthe memory a check is done to see if the received code is in fact a“supervisor code”. A portion or all of the supervisor code, which is tobe compared, is usually embedded in the read only memory of theprocessor. If a supervisor code is received the system will check anumber of further settings usually contained in the electricallyerasable memory. In most cases the most important check is to see if thesupervisor code is allowed to deactivate the system. In addition to thisa number of further actions may be taken if the correct command isreceived from the supervisor code coded key. A few examples may be theprogramming of new keys or the deletion of old keys from the memory.Changes in settings and operations may also be made with the supervisorkey

[0046] This is best explained by reference to the following examples. Ina code hopping system the code sent by the remote is usually a 65 bitbinary number. This data is encrypted for security and only a systemwith the correct decryption algorithm is able to decode the signal. Ifthe signal is decoded using the correct algorithm, a 32 bit number knownas the “fixed portion” of the code is available. This number isprogrammed into the encoder at time of manufacture. In a systemaccording to the invention, a dedicated number would be chosen torepresent a “supervisor code” coded key. This number would not be usedin the production of final consumer user code coded keys.

[0047] For example the supervisor code (In hex) could be 12,34,XX,XXwhere X is a variable. If the processor decodes the signal and finds thenumber is 12,34,XX,XX it knows it has received a supervisor code. Thebalance of the fixed code represented by XX,XX may be checked against avalue stored in non volatile memory to see if is the correct supervisorcode for that particular dealership.

[0048] This method can provide 65,534 different supervisor codes. Thismay be useful because one vehicle dealer should not have the same“supervisor code” as another dealer. In addition to this it providesadditional security. If one of the supervisor code coded keys is lost orstolen then the vehicles equipped with security system in the dealerslot may be programmed to not respond to the stolen supervisor code codedkey.

[0049] In the most preferred embodiment, a hierarchal system of codes isused. There is one dedicated master code that can be used to program thesecurity system to accept one of the supervisor codes (one of 65,534).In addition to being able to deactivate the security systems the mastermay be used to program a new user code coded key into the securitysystem, when the vehicle is sold to a customer.

[0050] For security, whenever a normal user code coded key is programmedinto the security system, the security system is configured to ignorethe supervisor code(s). This is to ensure that once the customer hastaken delivery of the vehicle it will not respond to a supervisor codecoded key. Although the supervisor code number is still stored in thesecurity system, a bit in the non volatile memory is set. Once this bitis set the security system will ignore a supervisor code if it isreceived.

[0051] In a simple, non code hopping system the supervisor code can beone or more dedicated codes. The same principles apply as with the codehopping system.

[0052] The hierarchical three tier master control system has number ofadvantages but the main one is the ability to take a standard securitysystem and have different levels of control of the system. It is alsopossible for the program to accept any one of 65,000 different mastercodes. The advantages are that all the systems that are produced areidentical. The supervisor code that they will respond to is onlyprogrammed in prior to delivery to a particular customer

[0053] The system works in three levels. At the top of the pyramid isthe master code coded key, followed by supervisor code coded keys andfinally user code coded keys. These coded keys all are in the form ofhand held push button remotes. The difference between the various typesis in the code they transmit to the security system.

[0054] Due to the proximity of car dealerships to each other and thecompetitive nature of the business, it is important for each dealershipto have a different supervisor code. It is important for this supervisorcoded remote be able to communicate with all the installed remotesecurity system immobilisers on the lot. The supervisor remote should beable to be used to reprogram user coded remote controls into theimmobilisers. Once a end user coded remote is programmed by thesupervisor remote into the immobiliser the supervisor codes areforgotten. The only way however, that a new user coded remote can becode in to the immobiliser is still via the original remote for thatdealership.

[0055] Further up the chain it is important before delivery to be ableto code the immobilisers with the supervisor code for the dealership. Todo this a master coded remote is provided which provides the precodedenvironment to accept the next hierarchy of supervisor coded remotes.

[0056] In the master coded remote, a Microchip code hopping, encryptedencoder is used. The decoding is performed in a Microchip 12C509microprocessor with an external non volatile memory (EEROM.) In theencoder a serial number is programmed in at time of manufacture. Thisserial number is known as the fixed portion of the code and usually notwo remotes are ever coded with the same code. In the security system ofthe embodiment, one specific code is designated to be the “master code”.If the microprocessor in the security system receives a valid signalfrom a coded key (remote control) it will first check to see if theencrypted part of the code is correct and then, if it is, will check theserial number. If the serial number matches a predetermined codedesignated to be a master code the security device will behave in adifferent manner and allow a number of programming options not allowedby other remotes.

[0057] For example in a 64 bit serial number, the master code could be11,22,33,44 in hex. If this code is received by the microprocessor(after decryption), the system will respond in a different way, allowingmore programming options to be performed. The number assigned to themaster coded key is embedded in the firmware of the microprocessor andis not changeable after production. Apart from the 64 bit code thesystem has a further 2 bits of information available. These are set bythe encoder and are dependent on two data lines. In the remote controlthese are connected to the activation switches. These switches incombination with the ignition switch give a total of 6 differentcommands that can be sent to the security system. In the systemdescribed only 4 are used.

[0058] An master coded key remote has the ability to do the following:

[0059] 1 Disarm the system

[0060] 2 Delete a master remote

[0061] 3 Program a new master remote

[0062] 4 Program in a user key

[0063] In the hierarchy, under the master coded key there are supervisorcoded key remotes. These have less privileges than the master coded key.They can do the following:

[0064] 1 Disarm the system

[0065] 2 Program in a user coded key

[0066] If a code is received by a security device, it is checked to seeif it came from a master coded key remote control. If it did not then itis checked to see if it is from a supervisor coded key remote. To dothis it checks a portion of the code. For example the a supervisor codecould be 10,10,XX,XX where XX,XX is one of 65,000 different mastercodes. When the microprocessor checks the received code and finds 10,10in the first 2 bytes it knows it has received a signal from a supervisorcoded key. It then goes and checks the remainder of the code(represented by XX,XX) against the supervisor code number stored in theEEROM. If this number is correct the microprocessor checks a bit in theEEROM to see if a supervisor coded key has permission to disarm thesystem. If it does then the system disarms. If not the code is rejected.

[0067] If the ignition is on at the time the microprocessor receives avalid supervisor code from the second button then it will allow eitheritself to be programmed back into memory or a new user key programmedinto memory.

[0068] User remotes can only arm and disarm the system. If a code isreceived by the microprocessor and it is not an master code nor is it asupervisor code, then the code, once decrypted is checked against a listof valid codes stored in the EEROM. If the code is found in the EEROMthen the system disarms. The only way the user coded key remote code canbe programmed into the EEROM is by means of either the master orsupervisor coded key remote controls.

[0069] This “Hierarchical Control System” allows the efficientprogramming of mass security systems for car dealerships, offers a nonclashing decoding environment for these businesses and further allowsrestricted reprogramming within each dealership with total control bythe distributor or engineering workshop.

[0070] In a vehicle dealership a number of security systems areinstalled into the vehicles on the lot. If a security system isinstalled the ignition keys may be left in the vehicle without fear ofthe vehicle being stolen because the vehicle will not start unless thesecurity system is first deactivated. A salesman wanting to demonstratea particular vehicle to a potential buyer must first deactivate thesecurity system. If the security system is “supervisor code enabled”then the salesman may use a supervisor coded key to deactivate thesecurity system allowing the vehicle to be demonstrated. The salesman'ssupervisor coded key would work on all vehicles with an installedsecurity system in the particular lot. With a short range system orpassively arming immobilisers, it would not be important if a fewvehicles in the vicinity of the operator were deactivated as the nontarget vehicles would re-arm within 30 seconds.

[0071] The advantage to the vehicle dealership is that they may leavethe keys in the ignition of the vehicle. This alleviates the problem oflocating the correct keys for the vehicle if a customer wishes to havethe vehicle demonstrated to them. A further advantage to the vehicledealership is the fact that many customers would want a security systemfitted to the vehicle when they purchase it. In this case the system isalready fitted and all that is required is for the master code to bedeleted from memory and individual user coded keys be programmed intothe security system before the customer takes delivery of the vehicle.

[0072] It should be appreciated that the scope of the invention is notlimited to the particular embodiment or application thereof describedherein.

1. A security system including a security device arranged to exertcontrol over a predetermined function, said security device beingresponsive to a coded key to exert control over said predeterminedfunction, said coded key and said security device communicating using adata string of a predetermined format, wherein said data string includesa predetermined portion thereof having settable values, wherein saidsettable values when within a first predetermined range of valuescorrespond to user codes assigned to user coded keys for said securitydevice, and said settable values when within a second predeterminedrange of values correspond to supervisor codes assigned to supervisorcoded keys for said security device, and said settable values whenwithin a third predetermined range of values correspond to user codesassigned to master coded keys for said security device, wherein saidsecurity system includes programming means allowing said security deviceto be programmable to be responsive to one or more said supervisor codedkeys and/or one or more said user coded keys, or one or more of saiduser coded keys only, wherein said supervisor coded keys have anintermediate level of access to said programming means between the levelof access of said master coded keys and said user coded keys.
 2. Asecurity system as claimed in claim 1 wherein said programming meansallows said security device to be programmable to be responsiveexclusively to one or more said supervisor coded keys, or exclusively toone or more of said user coded keys only.
 3. A method of providingsecurity against theft to a plurality of vehicles at a site, said methodincluding steps of providing a security system as claimed in claim 1,allocating said supervisor coded keys with supervisor codes specific tosaid site, installing a said security device in each of said vehicles atsaid site, and actuating said programming means to program each saidsecurity device to be responsive to said supervisor coded keys allocatedto said site for selectively immobilising and enabling operation ofvehicles, wherein all of said security devices are selectably responsiveto one or more supervisor coded keys allocated to said site.
 4. A methodas claimed in claim 3 wherein said security devices are responsive tosaid supervisor coded keys to actuate said programming means to programsaid security device to be solely responsive to code transmitted by oneor more specific said user coded keys.
 5. A method of providing securityagainst theft to a plurality of vehicles at a site, said methodincluding steps of providing a security system as claimed in claim 2,allocating said supervisor coded keys with supervisor codes specific tosaid site, installing a said security device in each of said vehicles atsaid site, and actuating said programming means to program each saidsecurity device to be responsive to said supervisor coded keys allocatedto said site for selectively immobilising and enabling operation ofvehicles, wherein all of said security devices are selectably responsiveto one or more supervisor coded keys allocated to said site.
 6. A methodas claimed in claim 5 wherein said security devices are responsive tosaid supervisor coded keys to actuate said programming means to programsaid security device to be solely responsive to code transmitted by oneor more specific said user coded keys.
 7. A coded key adapted for use inthe security system of claim
 1. 8. A coded key according to claim 7,wherein said key is selected from the group consisting of supervisorcoded keys, master coded keys, and user coded keys.
 9. A coded keyaccording to claim 8, wherein said key is provided in the form of aradio remote key.
 10. A security device adapted for use in the securitysystem of claim
 1. 11. A vehicle having a security device according toclaim 10 installed therein.
 12. A security system according to claim 1,wherein said security device is incorporated in a relay used to controla circuit essential for operation of the vehicle.
 13. A security systemas claimed in claim 12 wherein said programming means allows saidsecurity device to be programmable to be responsive exclusively to oneor more said supervisor coded keys, or exclusively to one or more ofsaid user coded keys only.
 14. A coded key adapted for use in thesecurity system of claim
 13. 15. A coded key according to claim 14,wherein said key is selected from the group consisting of supervisorcoded keys, master coded keys, and user coded keys.
 16. A coded keyaccording to claim 15, wherein said key is provided in the form of aradio remote key.